Tornadic waterspouts are simply tornadoes that form over water, or move from land to water. They have the same characteristics as a land tornado. They are associated with severe thunderstorms, and are often accompanied by high winds and seas, large hail, and frequent dangerous lightning.

Fair Weather waterspouts are usually a less dangerous phenomena, but common over the coastal waters along the Florida West Coast from late Spring through early Fall, and generally much more common than the tornadic variety.
The term fair weather comes from the fact that this type of waterspout forms during fair and relatively calm weather, often during the early to mid morning and sometimes during the late afternoon. Fair weather waterspouts usually form along dark flat bases of a line of developing cumulus clouds. This type of waterspout is generally associated with the formative stage of showers and non-severe thunderstorms whereas tornadic waterspouts develop in mature severe thunderstorms. Tornadic waterspouts develop downward in a thunderstorm while a fair weather waterspout begins to develop on the surface of the water and works its way upward. By the time the funnel is visible, a fair weather waterspout is near maturity.

Fair weather waterspouts form in light wind conditions so they normally move little. If a waterspout moves onshore, the National Weather Service issues a tornado warning as even these waterspouts have the potential to produce localized damage and injuries to people. Typically, fair weather waterspouts dissipate rapidly when they make landfall, and rarely penetrate far inland.

The best way to avoid a waterspout if boating is to move at a 90-degree angle to its apparent movement. Never move closer to investigate a waterspout. Some can still produce damage to you and your boat.

Waterspout Safety

Listen for special marine warnings about waterspout sightings that are broadcast on NOAA Weather Radio.

Watch the sky for certain types of clouds. In the summer, with light winds, look for a possible waterspout underneath a line of cumulus clouds with dark, flat bases. Anytime of the year, a thunderstorm or line of thunderstorms, can produce very intense waterspouts.

If a waterspout is sighted, immediately head at a 90 degree angle from the apparent motion of the waterspout.

Never try to navigate through a waterspout. Although waterspouts are usually weaker than tornadoes, they can still produce significant damage to you and your boat.